1. Field of the Invention
The present invention relates to an ink jet printer, and, more particularly, to setting a gap between a printhead and a print medium, i.e., a printhead gap, in an ink jet printer.
2. Description of the Related Art
It is generally known that improvements in ink jet printing can be achieved if the printhead can be positioned closer to the paper and if this gap distance between the printhead and the paper can be controlled within desired limits. An ink jet printhead moves or scans across the width of a sheet of paper, depositing ink drops onto the paper as the printhead scans. The printhead is generally slidingly coupled to a guide rod or shaft, which is oriented parallel to the direction of movement of the printhead. The printhead is coupled tightly enough to the guide rod that the straightness of the guide rod largely determines the straightness of the path of the printhead. Thus, the straightness of the guide rod partly determines the variations in the gap between the printhead and the paper, hereinafter referred to as the “printhead gap”, as the printhead scans. The straightness or flatness of the platen that supports the paper in opposition to the printhead also partly determines the variations in the printhead gap.
It is known to very precisely manufacture the guide rod with a high degree of straightness in order to limit variations in the printhead gap. It is also known to manufacture the platen very precisely with a high degree of straightness or flatness. Further, it is known to support the platen with one or more very precisely manufactured shafts having a high degree of straightness in order to provide the paper-engaging surface of the platen with a desired degree of straightness or flatness. A problem is that such precisely manufactured guide rods, platens and shafts are very expensive.
What is needed in the art is a method of dynamically adjusting the printhead gap while printing, thereby eliminating the need for expensive, precisely manufactured guide rods, platens and shafts.